ABSTRACT
Objective To observe the cardiosomatic motor reflex (CMR)of rats, and to clarify the descending modulation of nucleus raphes magnus (NRM)in cardiac nociception and its pathway.Methods 34 male healthy SD rats were randomly divided into NRM electrical stimulation group (n=8 ), NRM stimulation combined with dorsolateral funiculus (DLF ) transection group (n= 8 ), NRM stimulation combined with antagonist of 5-hydroxytryptamine (5-HT)methysergide intrathecal administration group (n=18).The rat model of CMR was established through inj ecting capsaicin into the pericardial sac of the rats in various groups. The electromyogram (EMG) response of dorsal spinotrapezius muscle was used as detection index, and by placing the stimulation electrode in NRM and (or)intrathecal catheterization, the descending inhibitory modulation of NRM in CMR and the influence of DLF tansection or methysergide intrathecal administration in descending inhibitory modulation of NRM were observed.Results Compared with before stimulation,the EMG response was decreased after NRM electrical stimulation (75 μA) (P 0.05 ). In addition, after intrathecal administration of methysergide,the EMG response after NRM stimulation was significantly increased compared with before intrathecal treatment of methysergide (P<0.05),but it was still significantly smaller than that of its control (P<0.05). Conclusion Cardiac nociception evoked by capsaicin stimulation is subject to descending inhibitory modulation from NRM,and the descending inhibition from NRM is conveyed via the DLF and partially mediated by endogenous 5-HT system.
ABSTRACT
Using immunocytochemical method and image analysis computer system, quantitative analysis of substance P (SP) containing nerve fibers and neurons in the nucleus of dorsolateral funiculus (NDLF) was studied in the rat spinal cord. Under light microscope, in the white substance of the whole length of the spinal cord, a concentrated triangular or cuneiform area of SP-immunoreactive positive fibers and cells could be observed in the NDLF region. Using the image anlysis computer system (IBAS 2000) the outline of the whole SP stained area in the NDLF was drawn with a light point of the Mouse and this whole area was measured and named as the reference area (REFAREA). We selected the optimal gray level of the image in NDLF region by the Interactive Segment as the threshold. The sum of the SP labelled areas was called the field area (FAREA). The ratio of the FAREA to REFAREA (AREA%) represented the percentage of density to area of the SP labelled substance in NDLF. The mean value of REFAREA, FAREA, and AREA% are: 47931.38?m~2, 21995.25?m~2, and 45.89% in the cervical segments; 31575.15 ?m~2, 7646.85?m~2, and 24.22% in the thoracic region; 26889.89?m~2, 8470.66?m~2, and 31.50% in the lumbar and sacral segments, respectively. In short, according to the density of SP positive fibers and neurons in NDLF and the size of their distributive area, the sequence of density and size from highest to lowest is: cervical, lumbar, sacral and thoracic segments, with the lowest one at thoracic 8-10 segments.
ABSTRACT
HRP solution was injected into the right side of the thoracic spinal cord of the rat with a micropipette to observe the neurons which give rise to the descending propiospinal tract. Labeled neurons were distributed throughout the bilateral Rexed's laminae Ⅰ-Ⅹ of the spinal cord in the segments rostral to the site of HRP application. The greatest number of the labeled cells were consistently found in lamina Ⅶ (including the intermediolateral nucleus), and then in laminae Ⅷ and Ⅳ. Our results verified the existence of the nucleus of the dorsolateral funiculus and its intraspinal connections in the spinal cord of the rat. This nucleus gives rise to the descending projections to the lower spinal segments.